Friction element and method of forming same



June 2, 1953 c. BERTOLET, JR 2,640,795

FRICTION ELEMENT AND METHOD OF FORMING SAME Filed Aug. 14, 1951 h mm nm Ma r 8 1 E Patented June 2, 1953 FRICTION ELEMENT AND METHODYQF EORMING. SAME -Elmer 0. 'Bertolet, Jr., Lititz, 'assignorto Raybestos-Ma-nhattan, Inc., ".Passaic, N. i J :a corporation of NewlJersey Application. August 14, 1951,,SerialN'o. 2.41355 7 Claims. 1

This invention relates to improvements in the production of friction elements and particularly .friction rings of the endless type suitable for .use

as automobile clutch jfacings, generally formed of'strips of material wound in spiral fashion to fform a coiled annulus.

.More particularly, the present invention is vdirecte'dlto the production of clutch "facings'wherein astrip comprised of asbestos, heat-hardenable binder, and friction. augmenting agents isshaped or foldedlongitudinally to impart to it an arouate, V-shape, ,or other deformed cross-section, prior to or while simultaneously coiling it spirally to form. an annulus, with internesting of'adjacent coils. This resultsina structure, after densifica- 'tion and cure vof the binder, which is devoid of any incipient or potential planes of cleavage .which'may extend directly'from one face ofthe "facing. to the opposite face thereof, and: thus has high resistance to tear'or'ruptureof thefacing when used in ccnjunctionwith engines which develop "high rotative speeds, as described, for

example, in United States Patent No. '2,096;692 to O. Cjilley, where employmentofwoven asbestos fiber is indicated.

.It; is an object of'thepresent invention to form friction "elements *of the foregoing class of novel composition and in an economical manner'by due *to ability to control thickness 'of' the hase andof the coatings applied thereto, and-of products of more uniformwei'ght from windings of the-"same-lengths of treated strip material.

Thus, in accordance with -thepresent inven- -tion,"I-'-' employ strips-cut fromwebs "or sheets of carded-asbestos fibers: of specific "formation and anovel manneras will hereinafterhe more particularly described.

The asbestos sheet material -which 'I =emp-Ioy is in general produced by carding and-dry felting-asbestosfiberso'f-spi nninggrade length's from a -mix which usually contains a percentage of cellulose-fibers to actas a carrier in the carding "operation. For use in friction" materials of the "class herein-contemplated, the cellulosefibersin .of' the total of the foregoing two kinds "of fibers. Examples of suitable cellulose fibers "arecotton,

rayon, flax, 'jute-fhemp, or the like. Although such cellulosefibers "have; a tendency to -carbonme on the 'operativesurface of "thefricti'on-- element under the frictional heat encountered; such surface carbon formation has been found -tocbe a desirable friction-modifying agent, particularly f'or'th'e purpose of minimizing the undesirable tendency-of fading under the fricti'onal'heat iii-operation; as is the'case when cellulose fibers are omitted.

Further objects and advantagesof the'present invention and the-details of construction thereof will be explained in connection withtherfollowing specification and accompanying diagram- *matic' drawings, wherein:

Fig. 1 is a plan view, wi th parts'brokensaway, of asheet of carded and condensedwebrofrfibrous asbestos sheet material impregnated withsaifriction material composition cement, in r accordance with the presentinvention.

Fig. 2 is a perspective View of astripacut from the impregnated sheet of Fig. 1, and -folded-lon- 'gitudinally prior to winding.

Fig. 3 'is-a-seetion of clutch facing Winding having-an inverted :V-shaped formation,-before compression and cure, and

*Fig. 4 is -a' similarview after compression. and cure.

5: is aview of-theface: or the clutchrfacing aftercompression and: cure.

Referring to the r drawings, the reference-numeral IEO; indicates: a web or sheet. oficardediand "condensed asbestos. material, composed :of the mixture of fibers previously indicated. Then-asbestosfibers-are of longer spinning grade'length such :as from ate 51 inch, and predominantly of. a. length=greater1than inch, as distinguished 'from the a shorter length. :fibcrs generally "emrpl'oye'dinmaking asbestos. paper inaqueous slur- =ries. yThe mixture of :fibersis carded in .a man- "ner we'llknown'to'the art through use of carding machinesxto fform -relatively thin webs with the fibers substantially uniformly distributed and lying a predominantlyndirecti-onalized,1 oriented and parallelized' formation, having individual '%.thicknesses ofz'from aboutr.003-. to x009 inch'before =29Il191l8flti011i0f pressure. vIf-- desired a plurality of :these web's .:maybeisuperimposed" to build: up the -=,.desir.ed ultimater weight or thickness of the desiredrsheet, and: in the-practic of the present invent-ioma; laminate of'two :or-more-.plies-' is generally'employed.

Two 'or more webs :are preferably I laid up; together-end then-jointly subi ecte'd" to-.-a sizing. op- :eratien wherein'athe material is totally immersed --in a -dilute solutionof a sizing or'bonding: material; and condensed by meansof rolls--so-as=to consolidate the' we'bi and to effect a uniform.-

tribution of said sizing or bonding material, and then dried. Such composites are relatively free from holes, lumps and other unevenness due to the leveling effect of multiple layers.

The sizing operation comprises the incorporation of conventional sizing, bonding or adhesive materials such as starches, latex, glues, shellac, aqueous solutions or dispersions of resinous materials such as urea, melamine or phenol formaldehyde resins, and the like, in the web to additionally strengthen the composite carded structure and to set it in its densified condition. The sizing operation is preferably so controlled as to incorporate from about one to about two per cent of solids in the web by weight thereof, and to thereby leave the web in a condition of porosity such that it can subsequently be readily impregnated with saturants. For example, the foregoing web material is of such porosity and absorbency that it can absorb three to four times the weight of impregnant that can be incorporated under like circumstances in a water-laid paper of comparable thickness. On the other hand the present consolidated web does not have the undue absorbency of a lofted or unsized web, and thereby permits employment of relatively low ratios of solvent to binder. In addition to the undesirable properties of lofted carded webs such as poor tensile strength, bulk, requirement for support and poor drying qualities, lofted webs require very high proportions of solvent to hinder solids for proper saturation and incorporation of equal amounts of solids.

In addition to the economies of the foregoing carded and condensed asbestos web material over Woven asbestos textiles, this web material is capable of production in finished thickness below that of conventional woven asbestos textiles and in a much more uniform condition, and can be more thoroughly and more uniformly impregnated. As previously indicated the same applies in general to water-laid fibrous asbestos papers, which have the added deficiency of low tensile strength and lack of deformability and distortability, as distinguished from the high tensile strength of the Web material herein employed, particularly in the direction of its fiber orientation, and its ability to appreciably stretch and be deformed without rupture which is of particular advantage for the purpose of the present invention as will hereinafter appear.

As one example of the material found suitable in the practice of the present invention, a mixture of 75% by weight of spinning grade asbestos and 25% by weight of cotton was carded and three plies laid together. This was then impregnated with a starch solution to incorporate 2% by weight of the starch, consolidated by rolling and dried, to form a sheet having a thickness of approximately .012 inch.

Before cutting the sheet in into strips and shaping, it is impregnated with a cement comprised of heat-hardenable organic binder and friction material fillers H, conventionally employed in friction material compositions. Such compositions in general comprise inorganic fillers such as litharge and barytes, and heat-hardenable binders, such as drying oils, thermo-setting synthetic resins, rubbers, and the like, generally, although not necessarily, as a mixture of two or more of such binders. The resins are generally of the phenolic type, such as the phenol aldehydes, particularly phenol formaldehyde, which may be of. an oil modified type. The rubber may be either natural rubber or a synthetic rubber such Rubber 7.40

Accelerator .22 Sulphur 7.92 Barytes 3 1.90 Litharge 24.90 Graphite 1.62 Rosin 1.08 Phenolic resin 25.06

The web material is preferably impregnated and saturated by passing it through the cement solution and excess removed by suitable means, such as squeeze rolls, and then dried to remove the solvent but without cure of the binder. The total amount of the binder solids is approximately equal to the weight of the fibrous materials, or from about 40 to about 60% by Weight of the composite.

The impregnated sheet material is then cut into strips of for example one-half inch in width, with the oriented fibers running generally longitudinally of the strip, and then longitudinally, shaped or deformed, to for example the strip E2 of Fig. 2 having an inverted V-shape cross-section. This shaped strip is thereafter helically Wound with adjacent coils in internesting relationship to form the annulus of Fig. 3 by suitable means and in the manner indicated in the aforesaid patent. Due to the elastic nature of the web base, its high tensile strength and directionalized fiber formation it may be conveniently stretched without rupture in the shaping and Winding operations and has adequate elasticity or stretchability required for elongation of the shaped strip at the apex of the V, and for ready contraction at the edges of the strip when wound as shown in Fig. 3, or conversely if it were to be Wound with the apex of the V inwardly, or any other desired symmetrical cross-section.

The coiled annulus is therefore subjected to heat and pressure by suitable means, such as, for example, in a mold to densify it, and cause the binder to flow to permeate and consolidate the windings, and to heat-harden or cure the binder content, after which the unit is subjected to a finishing operation, such as by surface grinding. The rivet holes (3 may be formed during the molding operation or formed subsequently by drilling and counter-boring.

It will be understood that although I have in the foregoing described the preferred embodiment of my invention, as non-fully equivalent alternative, I may employ fiat wound coils of the same tape or strip composition, since even in such case the economy of the carded asbestos web material over woven textiles is inherent, and its employment has the advantage of ability to control desired thickness of base material and amount of impregnant, and greater uniformity of surface and thickness than water-laid asbestos papers or woven asbestos textiles, and the ability to be better and more uniformly saturated with impregnants than such materials.

I claim as my invention:

1. An endless clutch facing comprised of a spirally wound strip of thin, flexible, consolidated and condensed carded long fiber asbestos web material of relatively high porosity, the fibers extending generally longitudinally of the strip, said strip being longitudinally folded to provide a symmetrical cross-sectional form and the coils thereof being secured together in internesting relationship.

2. An endless clutch facing comprised of a spirally wound strip of thin, flexible, consolidated and condensed carded long fiber asbestos web material of relatively high porosity including cellulose fibers in the proportion of from 10% to 45% by weight of said fibers, the fibers extending generally longitudinally of the strip, said strip being longitudinally folded to provide a symmetrical cross-sectional form and the coils thereof being secured together in internesting relationship.

3. A friction element suitable for use as a clutch facing, comprising an annular body formed of a convoluted strip of consolidated and condensed carded asbestos fibers of spinning grade length including cellulose fibers in the proportion of from 10% to 45% by weight of said fibers, said strip being of relatively high porosity and the fibers thereof being generally oriented in a direction longitudinally of said strip, said strip includin heat-'hardenable binder, said element being compressed to consolidate the convolutions upon each other and heat treated to harden the binder.

4. A friction element suitable for use as a clutch facing, comprising an annular body formed of a convoluted strip of consolidated and condensed carded asbestos fibers of spinning grade length including cellulose fibers in the proportion of from 10% to 45% by weight of said fibers, said strip being of relatively high porosity and the fibers thereof being generally oriented in a direction longitudinally of said strip, said strip being impregnated with a heat-hardenable binderfriction material filler composition cement, said element being compressed to consolidate the convolutions upon each other and heat treated to harden the binder.

5. A friction element suitable for use as a clutch facing, comprising an annular body formed of a convoluted strip of consolidated and condensed carded asbestos fibers of spinning grade length and including cellulose fibers in the proportion of from 10% to 45% by weight of said fibers, the fibers of said strip being generally oriented in a direction longitudinally thereof,

said strip being of a relatively high porosity and impregnated throughout its thickness with a heat-hardenable binder-friction material filler composition cement, said strip being further longitudinally folded to provide a symmetrical cross-sectional form and the convolutions thereof being in internesting relationship, said element being compressed to consolidate the convolutions upon each other and heat treated to harden the binder.

6. The method of forming a friction element suitable for use as a clutch facing, which oomprises impregnating a strip of relatively thin, porous, flexible asbestos sheet material composed of carded and condensed spinning grade asbestos fibers substantially uniformly distributed and directionalized longitudinally of the strip, with a heat-hardenable binder-friction material filler composition cement, drying solvent content from said cement, convolutely winding said strip material to form an annular body, and subjecting said body to heat and pressure to consolidate said strip.

7. The method of forming a friction element suitable for use as a clutch facing, which comprises cutting a sheet of relatively thin, porous, flexible asbestos sheet material composed of carded and condensed spinning grade asbestos fibers including cellulose fibers in the proportion of from 10% to 45% by weight of said fibers wherein the fibers are substantially uniformly distributed and lie in a predominantly oriented and parallelized formation, into strips wherein the fibers extend generally longitudinally of the strip, impregnating said strip throughout its thickness with a heat-hardenable binder-friction material filler composition cement, drying solvent content from said cement, folding said strip longitudinally to provide it with a symmetrical crosssectional form, convolutely winding said strip material to form an annular body, and subjecting said body to heat and pressure to consolidate the convolutions upon each other and to harden the binder.

ELMER C. BERTOLET, JR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,420,883 Stanley June 27, 1922 1,437,438 Nanfeldt Dec. 5, 1922 1,465,389 Fisher Aug. 21, 1923 1,771,749 Eisenhardt July 29, 1930 2,096,692 Cilley Oct. 19, 1937 2,218,535 Judd Oct. 22, 1940 2,264,901 Gosling Dec. 2, 1941 2,546,056 Batchelor Mar. 20, 1951 

1. AN ENDLESS CLUTCH FACING COMPRISED OF A SPIRALLY WOUND STRIP OF THIN, FLEXIBLE, CONSOLIDATED AND CONDENSED CARDED LONG FIBER ASBESTOS WEB MATERIAL OF RELATIVELY HIGH POROSITY, THE FIBERS EXTENDING GENERALLY LONGITUDINALLY OF THE STRIP, SAID STRIP BEING LONGITUDINALLY FOLDED TO PROVIDE A SYMMETRICAL CROSS-SECTIONAL FORM AND THE COILS THEREOF BEING SECURED TOGETHER IN INTERNESTING RELATIONSHIP.
 6. THE METHOD OF FORMING A FRICTION ELEMENT SUITABLE FOR USE AS A CLUTCH FACING, WHICH COMPRISES IMPREGNATING A STRIP OF RELATIVELY THIN, POROUS, FLEXIBLE ASBESTOS SHEET MATERIAL COMPOSED OF CARDED AND CONDENSAED SPINNING GRADE ASBESTOS FIBERS SUBSTANTIALLY UNIFORMLY DISTRIBUTED AND DIRECTIONALIZED LONGITUDINALLY OF THE STRIP, WITH A HEAT-HARDENABLE BINDER-FRACTION MATERIAL FILLER COMPOSITION CEMENT, DRYING SOLVENT CONTENT FROM SAID CEMENT, CONVOLUTELY WINDING SAID STRIP MATERIAL TO FORM AN ANNULAR BODY, AND SUBJECTING SAID BODY TO HEAT AND PRESSURE TO CONSOLIDATE SAID STRIP. 